SYNOPSISAnacystis nidulansdisappeared rapidly from culture in the presence of an unidentified species ofOchromonas.Disappearance was light‐independent and could be induced neither by bacteria associated with, nor by soluble products released from the flagellate. Electronmicrographs of mixed cultures revealed numerousA. nidulanscells in various stages of digestion within vacuoles ofOchromonas.Evidently the disappearance of the alga from culture resulted from phagotrophy by the chrysomonad. A 2‐stage digestive process is suggested wherebyA. nidulanscells are initially sequestered in the posterior “leucosin” vacuole and then undergo the terminal stages of digestion and elimination in smaller, peripheral v